Since the cutting teeth of such a suction head are prone to wear, they should be readily replaceable. For this purpose it is known to provide the welded-on tooth anchors and the teeth themselves with aligned slots to be traversed by removable retaining keys. For proper alignment, the teeth and their anchors are to have interfitting formations which usually are designed as scalloped or crenellated ledges on the anchor and lobes on the tooth projecting into the indentations defined by the crenellations. The crenellated ledge forms a rim of a base by which the anchor is to be welded onto the periphery of the suction head, this rim surrounding a head which projects from the base beyond that rim and tapers toward a remote tip so as to fit into a complementary concavity of the tooth. The head has a throughgoing slot in line with two diametrically opposite indentations in order to receive a retaining key passing through similar slots in corresponding lobes of the tooth.
In many instances the base of such a tooth anchor, on the one hand, and its head with the crenellated rim, on the other hand, are manufactured as separate parts to be subsequently welded together; the part comprising the head and the rim is sometimes referred to as a welded-on nose. This latter part may be unitarily cast or forged; the key slot, in either case, is produced by machining. It has also been proposed to cast the entire tooth anchor in one piece.
Tooth anchors made by any of these conventional processes have only a limited service life and are liable to crack, sooner or later, at the weld joint (if any) between the base and the nose or at the key slot. These tooth anchors, accordingly, are not well suited to withstand the stresses resulting from the demands of the industry for dredges with ever-increasing shaft power which nowadays may have to reach about 2200 hp or more, lying in a range which is some 25% higher than what was required not so long ago.